5 Use of biological resources

Question 1

What can be used to increase the yield of certain crops?

Answer 1

Glasshouses
Polythene Tunnels

Allow control over limiting factors of photosynthesis

Question 2

Increasing the yield of crops: Glasshouses or Polythene tunnels

Answer 2

• Paraffin Heater (optimum temp. for enzymes, produces CO2 as it burns)
• Artificial lighting (plants don’t have to stop photosynthesus at night)
• Prevents entry of pests

Question 3

How does fertiliser increase the crop yield?

Answer 3

When plants don’t have enough minerals, their growth + life processes are effected.
Sometimes the soil has ran out of the mineral as it has been used by a differnt crop
So fertilisers provide minerals.

Question 4

Reasons for pest control

Answer 4

Pests feed on crops, damaging them, reducing their yield

Question 5

Advantages of Pest Control

Answer 5

Less plants damaged by pests -> increases crop yield

Question 6

Disadvantages of Pest Control

Answer 6

Chemical, poisonous to humans so must use very little to avoid harming other wildlife

Question 7

Biological Control

Answer 7

Alternative to pesticides
Using other organisms to reduce pests

Question 8

Advantages of Biological Control

Answer 8

Longer - lasting effect
Less harmful to wildlife

Question 9

Disadvantages of Biological Control

Answer 9

Can become a major pest themselves

Question 10

Role of yeast in the production of food including bread

Answer 10

1. Bread dough contains flour, water and sugar and yeast
2. When left to rise, enzymes break down the carbs into sugar, and this sugar is used in aerobic respiration (produces CO2)
3. When the oxygen runs out, anaerobic respiration occurs instead. Produces CO2 (air pockets) an ethanol = fermentation.
4. These air pockets expand -> bread rises.
5. When put in the oven, fermentation continues until enzymes are denatured. Ethanol evaporates away.

Question 11

5.6 practical: investigate the role of anaerobic respiration by yeast in different conditions

Answer 11

1. Mix together sugar, yeast and distilled water in text tube
2. Add layer oil to make sure anaerobic respiration occurs
3. Seal with bung and attach with delivery tube connecting to test tube of water.
4. Put 1st test tube in water bath and count bubbles produced.
5. No. of bubbles/time taken = rate of CO2 production = rate of anaerobic respiration
6. Repeat experiment with different temperature water baths

Can be improved by using a gas syringe instead of water tube.

Question 12

Fermentation

Answer 12

When microorganisms break down starch to produce energy

Question 13

Production of yogurt

Answer 13

1. Sterilise equipment to remove unwanted microbes + chemical contamination
2. Milk is pasteurised at 85 -95 degrees for 12-30 minutes
3. It is then homogenised
4. Milk is cooled then Lactobacillus is added
5. Mixture of milk + lactobacillus is incubated
6. Thickened yogurt is stirred and cooled

Question 14

Why is milk pasteurised?

Answer 14

To kill unwanted bacteria to avoid competition for lactose with lactobacillus

Question 15

Why is milk homogenised?

Answer 15

To disperse fat
The longer it is homogenised for, the lower fat yogurt

Question 16

Why is milk cooled before Lactobacillus is added?

Answer 16

So that enzymes do not denature

Question 17

Why is the milk incubated?

Answer 17

Lactobacillus digests milk proteins + ferments the lactose sugars to form lactic acid
Increases acidity/lowers pH to prevent growth of other harmful microbes + thickens milk to yogurt

Question 18

Fermentors

Answer 18

To grow microorganisms in large quantities

Question 19

Parts of Fermentor

Answer 19

• Input for microbial culture
• Paddle Stirrer
• Gas outlet
• Probes (pH and temperature)
• Stainless steel vessel walls
• Water jacket
• Air inlet

Question 20

Process of Natural Selection

Answer 20

1. There is variation within the organisms of a species
2. Changing conditions in the environment favour a characteristic over others
3. Those better adapted to the environment survive and reproduce + become more common in the population
4. Those less adapted to the environment die

Question 21

What is natural selection

Answer 21

Life started at simple organisms from which all large complex organisms evolved